Interconnection of lead parts



United States Patent US. Cl. 29-488 2 Claims ABSTRACT OF THE DISCLOSURE Lead parts are interconnected by treating them electrochemically to clean them, and then dipping them into molten lead.

It is known to interconnect lead parts by dipping them into molten lead. The effectiveness of this technique depends on the lead parts being clean, and the present invention provides a method of pretreating the parts without the necessity of mechanical cleaning or the use of a flux. A method according to the invention comprises treating the parts electro-chemically to clean them.

In one example, a lead part to be cleaned prior to welding is immersed in an electrolyte which can be a solution of an acid, an alkali or an ionic salt. A second electrode, which can be lead or any other metal which is insoluble in the electrolyte, is also immersed in the electrolyte. A voltage is applied between the two electrodes so that the article to be cleaned is the cathode, and the second electrode is the anode. As a result of the passage of current, the lead compounds present on the article to be cleaned are reduced to metallic lead. The minimum quantity of electricity which must be passed to reduce all the compounds present to lead can be calculated if the weight and approximate composition of the contaminant is known. However, not all the current is used in this way, because other processes, for example the evolution of hydrogen, may take place at the same time. For this reason, the actual quantity of electricity required has to be found empirically.

As the resultant surface of the part to be cleaned consists of finely divided lead, it is usually necessary to include an oxidation inhibitor in the electrolyte to prevent 'ice vre-oxidation of the surface. Suitable compounds for use as oxidation inhibitors are phenols or other known surfaceactive agents.

In one specific example, the electrolyte was 5% sulphuric acid, the anode was lead, and the oxidation inhibitor was hydroquinone. The cathode was maintained at a voltage of -2.0 volts as compared with a saturated calomel reference electrode, and a reduction time of one minute or less was found to be necessary depending on the amount of contaminant present on the lead part.

In a second example, the electrolyte used was 5% sodium hydroxide, and the cathode was held at 2.0 volts. The remaining conditions were as specified in the first example. In this example, suitable inhibitors are nitroguanidine, morpholine, glucose, phenol and stearic acid.

In some instances, more than one cathodic treatment may be required.

After cleaning, the interconnection is completed by dipping the parts into molten lead in known manner.

Having thus described our invention what we claim as new and desire to secure by Letters Patent is:

1. In a process of interconnecting elements made from lead including cleaning the elements and subsequently immersing the cleaned elements into a bath of molten lead; the improvement wherein the cleaning step comprises impressing electric current across the elements and an anode so as to make said elements perdominantly cathodic while immersing said elements and said anode in an aqueous electrolyte capable of electrolytically reducing lead oxides and continuing said current until said oxides are substantially reduced to free lead.

2. A method as claimed in claim 1 wherein the electrolyte includes an oxidation inhibitor.

References Cited UNITED STATES PATENTS 172,956 2/1876 Benton 29-503 600,250 3/1898 Reese .a 29503 699,592 5/1902 Thompson 29-484 3,410,771 11/1968 Sudrabin et al. 204

ROBERT K. MIHALEK, Primary Examiner US. Cl. X.R.

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